Lyme borreliosis is a tick borne infection caused by Borrelia burgdorferi which causes a multisystem disorder of the skin, nervous system, heart and/or joints. The disease was first recognized in 1975 and treatment recommendations have evolved since its discovery and methods were available to diagnose the condition. Patients infected before 1988 were either not recognized, treated late, or treated with antibiotics which would not be expected to penetrate the central nervous system or the joints. Newly diagnosed cases and some cases in areas where Lyme disease is not common are also at risk for developing late manifestations. This study will determine the cumulative prevalence of acute, chronic (persistent) and asymptomatic Lyme disease in a defined population exposed to Borrelia burgdorferi, identify potential risk factors for development of chronic Lyme, establish a population-based longitudinal cohort of Lyme disease and identify cases for controlled drug trials of chronic Lyme. Tick infested census tracts identified by tick and veterinarian studies will be surveyed for subjects with chronic symptoms which might be Lyme. A screening evaluation will be done in the community and patients with possible or definite chronic Lyme disease and a control group of asymptomatic individuals will be evaluated so that they can be classified definitively. Some patients will be referred to three existing NIH sponsored drug trials for chronic Lyme disease. The entire cohort will be followed every 3 years.